The invention relates to a packaging envelope for the packaging of objects, in particular of meat, but also of other objects which are to be vacuum-packed. Such packagings customarily envelop the objects loosely at first, and the air is then withdrawn from the packaging envelope by special measures so that the envelope, due to the external air pressure, wraps itself closely round the object.
Such a vacuum packaging of objects is very involved, as the air first has to be removed from the envelope after insertion of the object into the envelope, after which the ends of the envelope are closed, for example welded, so that the packed object with the envelope closely wrapped round it is vacuum-packed in standard terminology. The closing of the ends of the envelope needs to be done at one side only if the envelope is formed as a bag.
In the case of meat, it is often of advantage to force the meat into an approximately round cross-sectional shape, in particular an approximately circular cross-sectional shape. For this purpose the provision of elastic netting is known (FR-PS 1 560 425, EP 0 175 173 A1, U.S. Pat. No. 4,155,212, CH-PS 662 543 A5). Moreover devices for filling the meat into this netting are known (U.S. Pat. No. 4,155,212).
Such netting serves to keep the filled-in joint of meat in its shape and also to press it into a shape which has an approximately circular cross section. This applies in particular to pork such as Casseler or rolled pork.
If the meat is introduced into expandable rubber netting according to the prior art, a very great tension is applied to the meat in radial direction to the center line of the packaging after introduction into the rubber netting, i.e. the threads of the netting leave the meat in the cross-sectional round shape or even press it into a round cross-sectional shape if the original joint of meat was not round. This also applies when the meat is tied by means of cords or the like.
Netting is, however, not packaging within the meaning of the invention, as the air and any other contaminant can reach the packed commodity without hindrance through the meshing of the netting.
For shaping meat into a round form, such netting or tying procedures could also be applied in principle to beef (roast beef, fillet of beef or the like). This is, however, not economically efficient and raises the wholesale price substantially. Tying procedures are not consumer-friendly because the tying material has to be removed prior to the meat being sold and imprints and possibly damage are left on the meat by the tying. If the meat is to be protected from external influences, which is normally the case, it must be packed in addition when netting is used.
A further disadvantage is that the threads of the netting often adhere to the meat, so that the surface of the meat is damaged on detachment of the netting. For this reason a backing (CH-PS 662 543 A5) has already been provided between netting and meat surface, as has an edible gelatin layer (EP O 175 173 A1). These backings do not contribute towards shaping the meat, nor do they press the air between envelope and meat out automatically, because the cords of the netting contact the meat closely and, even if an envelope is enclosed in the elastic netting, air pockets remain in the envelope in the meshing of the netting.
Moreover, the rubber cords of the netting cause meat juice to escape because the cords of the netting contact the meat linearly and exert great pressure on the meat along these lines.
U.S. Pat. No. 4,155,212 shows a device for packaging meat. Various envelopes are proposed as packaging material:
a) Elastic Netting
This elastic netting is not a packaging for the reasons stated above and is therefore eliminated. b) Monoplane Material
If a flexible material is meant with this material according to U.S. Pat. No. 4,155,212, then this material is verifiably not usable on the packaging device described in U.S. Pat. No. 4,155,212 because such an envelope cannot be withdrawn from the tube through which the meat is pushed. For the envelope must be placed with great pre-tension on the tube so that is contracts elastically after being withdrawn from the tube. In this configuration the envelope sticks, as it were, on the tube and cannot be withdrawn from the tube. It has been shown that the envelope tears in this process. But even if a use of a elastic foil as packaging for the meat were to be made possible by modifying the packaging device, this foil is not suitable for serving as vacuum packaging as this material is not gas-impermeable. Gas-impermeability is attained only in connection with a second foil serving as a gas-impermeable layer in interaction with a first elastic foil according to the invention.
It is the object of the invention to provide a packaging envelope or a packaging bag which contracts after introduction of the commodity into the envelope or the bag in such a way that the air between the filled-in commodity and the envelope is pressed out automatically.
It is the second object of the invention to provide a packaging which induces a shaping of the contents into an approximately circular shape, which simultaneously packages the contents, in particular the meat, i.e. provides protection from external influences.
It is the third object of the invention to maintain this attained approximately round cross-sectional shape even for a lengthy storage period.
It is the fourth object of the invention to maintain the attained air exclusion after the closing of the envelope or of the bag (vacuum packing) even for a lengthy period, i.e. to prevent the ambient air from migrating through into the packaging.
All these objects are solved according to claims 1 and 2.
Due to the genuine elasticity of the packaging material, the air between contents and packaging is forced out in that the packaging material wraps itself closely round the contents closely. The subsequently resulting radial tension of the packaging envelope or of the packaging bag on the contents causes a shaping of the contents into a round (circular) cross section. As this radial tension is also retained in the long term in the case of genuine elasticity, this tendency to round shaping is also retained throughout the storage period, and an exchange between ambient air and contents after the closing of the packaging is prevented even for a length period by the second foil as a gas-impermeable layer.
In a further configuration of the invention, the packaging can be formed in such a way that foods in particular can be packed in it, i.e. so that the foil (layer/ply) of the packaging envelope or of the packaging bag coming into contact with the filled-in food consists of a food-compatible material. This foil (layer/ply) can consist of a correspondingly selected plastic material, whereby the food-compatibility of a plastic depends on the type of food to be packed, because each food reacts differently to the composition of the plastic.
If the gas-impermeable layer comes into contact with the food, it must be food-compatible. If the gas-impermeable layer itself is not food-compatible, the packaging envelope can have a third foil (layer/ply) which is provided inside the envelope and imbeds the gas-impermeable layer, as it were. This foil (layer/ply) then comes into contact with the food in the packaging process and must be food-compatible.